Developers of elastic shoes and shoe soles are confronted with the problem of back injury and releasing the stored energy in the shoe sole in a manner which improves walking and running economy while at the same time achieving adequate bio-mechanical shoe stability and cushioning. Many shoe manufacturers have concentrated their effort on shock absorption by increasing the thickness of the shoe sole. This has resulted in a slight change of the angle between the ankle and the foot that may weaken the tendons of the foot. This change of the angle may also lead to instability and reduced bio-mechanical effect.
Many efforts have been made to develop an effective spring mechanism for the shoe or shoe sole. However, the earlier proposed spring designs for shoe soles have not been entirely satisfactory. Despite many elaborate shoe sole solutions, back injuries and other injuries are still common due to poorly designed shoes. Injuries due to poor shoe designs are particularly common in sports and heavy duty work activities.
One important function of a shoe, such as a running shoe, is to protect the foot from the stresses of running. The forces and motions that occur in different sports vary greatly. Because of these differences it is important that active participation in varied sports require varied shoes. For example, tennis and other racquet sports require much side-to-side motion and the shoe must provide lateral stability. If the shoe is unstable and has high heel elevation when the athlete is moving from one side to another the likelihood is great the athlete may suffer an ankle sprain. The majority of shoes are not well designed. Some insufficiencies of the current shoe designs may be overcome by the present invention.
The shoe system of the present invention comprises a shoe that has a toe section and a heel portion. A shoe sole is disposed inside the shoe and has a groove defined therein. The groove extends angularly from an upper surface of the shoe sole rearwardly towards the heel portion of the shoe. A wedge section is removably attached to the shoe sole. A removable shoe insert has a stiff first member and a resilient second member attached to the first member. The second member maybe inserted into the groove. The second member has one side that may be thicker than the opposite side so that the second member is only twistable in one direction. The stiffness difference may also be achieved by attaching flexible member at an angle relative the longitudinal direction of the shoe insert.